Conventionally known organosilicon compounds for use in the modification of surface properties of polyurethanes or polyesters include compounds of formulas (1), (2) and (3), having a hydroxyl group or an organic group having a hydroxyl group at both ends of polydimethylsiloxane, and compounds of formula (4) having an organic group having two hydroxyl groups different in reactivity at one end of polydimethylsiloxane. ##STR2## wherein Me represents a methyl group, and l, m and p each represents a positive integer.
However, modification of a polymer by the siloxane compound having a hydroxyl group at both ends thereof has the following problem. That is, since the whole siloxane segment is introduced into the resulting polymer, the siloxane compound should be used in a considerably large proportion for attaining sufficient modification of surface properties of the final resin molded articles.
The above problem is overcome with the compound of formula (4) as disclosed in, for example, JP-A-62-195389. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".) However, the two hydroxyl groups of this compound greatly differ from each other in reactivity because the compound has a structure in which one of the two hydroxyl groups is bonded to a primary carbon atom and the other is bonded to a secondary carbon atom. For this reason, when this compound is used, not only do copolymerization reactions proceed, with difficulty but there is another problem that a polymer having the intended molecular structure cannot be obtained.